1970/80s Jules Verne-inspired bizarre underwater city / submarine abduction [closed]

I am looking for a movie I saw as a child in the 1980s on German TV. Sadly my memory is somewhat blurrish.

I remember a "20000 leagues under the sea"-inspired story, featuring the main characters being abducted into a submarine or underwater city.

It was a live-action color movie with a distinct steam fantasy feel. Most likely not a German but a dubbed foreign movie, and I remember a rather high production value. Likely made in the 1970s or 1980s.

I most dominantly remember that it featured antagonists with large, bizarre moustaches. The most memorable image is that in the end, a lot of people die in an over-the-top (still suitable for minors) fashion, with one being pierced by a cello or double bass.

The whole movie had a humorous but also rather grotesque, silent-film-era feeling to it.

I'm afraid that's all I have to go on. Any hints appreciated.

Update: Given the considerable difficulty in finding this movie, it is quite possible that it was a former Eastern Bloc production. The closest I could find in tone and style is Vynález zkázy (The Fabulous World of Jules Verne) from 1958 (IMDB, Trailer), but that is not it.

Update: It is none of the works listed at Wikipedias' Adaptations of Twenty Thousand Leagues Under the Sea.